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Supported catalyst with a defined pore distribution in the mesopore rangeRelated Patent Categories: Catalyst, Solid Sorbent, Or Support Therefor: Product Or Process Of Making, Forming Or Treating A Sphere, Process OnlySupported catalyst with a defined pore distribution in the mesopore range description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070191212, Supported catalyst with a defined pore distribution in the mesopore range. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to a supported catalyst, processes for producing it and processes for the metathesis of nonaromatic unsaturated hydrocarbon compounds using the supported catalyst. [0002] It is generally known that the pore structure of supported catalysts is of critical importance for their activity. This is particularly true of supported catalysts which are used for the metathesis of nonaromatic unsaturated hydrocarbon compounds. [0003] The metathesis of nonaromatic unsaturated hydrocarbon compounds is a long-established method of breaking and reforming C--C bonds (e.g. Mol, J. C., Chapt. 4.12.2 "Alkene Metathesis" in "Handbook of Heterogeneous Catalysis", Eds. Ertl, G., Knozinger, H., Weitkamp, J., VCH, Weinheim 1997; Weissermehl, K., Arpe, H.-J., Chapt. 3.4 "Olefin-Metathese" in "Industrielle Organische Chemie", 4th Edition., VCH, Weinheim 1994). Various types of catalysts for a heterogeneously catalyzed metathesis have been described. For the temperature range up to about 120.degree. C., the use of supported Re.sub.2O.sub.7 or Re(CO).sub.10 catalysts is customary (Mol, J. C., Chapt. 4.12.2 "Alkene Metathesis" in "Handbook of Heterogeneous Catalysis", Eds. Ertl, G., Knozinger, H., Weitkamp, J., VCH, Weinheim 1997). [0004] DE-C-3823891 and EP-A-90994 disclose the preparation of an aluminum oxide which has a maximum of the distribution function of the pore diameters in the mesopore range at above 0.008 .mu.m. Apart from numerous other applications, the general use as support material for catalysts is mentioned. [0005] Re-containing catalysts in which no attention is paid to the pore structure are described, for example, in U.S. Pat. Nos. 3,641,189 and 3,642,931. However, these catalysts deactivate rapidly, which makes frequent regeneration necessary. A slurry of the deactivation makes industrial implementation considerably easier. In addition, a high activity is desirable in order to utilize the noble metal used as effectively as possible. [0006] It was an object of the present invention to provide porous supported catalysts which have a specific pore structure and maintain a high activity over a very long period of use. In particular, catalysts which are suitable for the preparation of nonaromatic unsaturated hydrocarbon compounds by metathesis are to be provided. [0007] We have accordingly found a supported catalyst comprising a support (S) in which Al.sub.2O.sub.3 is present in a proportion of at least 75% by weight and a rhenium compound as active component (A), wherein the maximum of the distribution function of the pore diameters in the mesopore range is at from 0.008 to 0.050 .mu.m. [0008] The support material (support S) for producing the supported catalysts comprises at least 75% by weight of gamma-Al.sub.2O.sub.3. Depending on the calcination temperature, amounts of other phases such as alpha-, eta-, delta- or theta-Al.sub.2O.sub.3 can also be present. The ratio of the various phases to one another is not critical, although the proportion of alpha-Al.sub.2O.sub.3 is preferably kept as low as possible (preferably less than 10%). For the purposes of the present invention, calcination is heating in an oxidative gas atmosphere, e.g. a gas atmosphere comprising more than 20% by volume of oxygen and otherwise inert constituents. The preferred gas atmosphere is air. [0009] In one variant of the production process, the catalysts having the desired pore structure are obtainable by using supports (S) having a maximum of the distribution function of the pore diameters in the mesopore range at from 0.008 to 0.050 .mu.m in the production process and the catalyst is produced by customary methods from these supports (S) and an active component (A) using customary auxiliaries if appropriate. [0010] To produce such supports (S) having a maximum of the distribution function of the pore diameters in the mesopore range at from 0.008 to 0.050 .mu.m, a particularly useful process is one in which aluminum alkoxides occur as intermediate. The synthetic aluminum oxide precursors produced by such a route allow the mesopore size to be set in the specified range. According to DIN 66 134 of February 1998, published by the Deutsche Institut fur Normung e.V., mesopores are pores having sizes from 2 to 50 nm. [0011] In this specific process, an aluminum alkoxide is aged at a water vapor pressure of from 1 to 30 bar and a temperature of from 100 to 235.degree. C. for from 0.5 to 20 hours while stirring at a circumferential velocity of from 1.0 to 6.0 m/s to form a synthetic aluminum hydroxide. This is then usually dried by a customary method. This process and further details regarding it are known from DE-C-3823895. [0012] In many cases, the supports (S) can be in the form of spherical shaped bodies. These can be obtained particularly advantageously by [0013] preparing an alumina sol from a synthetic aluminum hydroxide prepared as described above by suspending the synthetic aluminum hydroxide in dilute mineral acid having a concentration of from 1 to 5% and subsequently adding from 1 to 10% by weight, based on the total weight of the sol, of urea, [0014] introducing the alumina sol dropwise into a shaping column whose lower part is filled with aqueous ammonia solution, and [0015] drying the spherical particles formed in the shaping column. [0016] The alumina hydrate used here is preferably obtained by hydrolysis of an aluminum alkoxide. This preparative process and further details regarding it are known from EP-A-90994. [0017] Apart from aluminum oxide, the support (S) may, if appropriate, further comprise additional customary support materials, preferably materials selected from the group consisting of SiO.sub.2, aluminosilicates, TiO.sub.2, ZrO.sub.2, MgO, CeO.sub.2 and ZnO. [0018] To improve the physical properties of the catalyst, further lubricants and additives in addition to the actual support material can also be mixed in, e.g. graphite, cement, gypsum or muscovite. [0019] Suitable supports (S) typically have a specific surface area of less than 280 m.sup.2/g, preferably from 70 to 250 m.sup.2/g, particularly preferably 100-200 m.sup.2/g. Suitable pore volumes (determined by means of mercury porosimetry) are usually in the range from 0.25 to 1.3 ml/g, preferably from 0.35 to 1.0 ml/g. The preferred water absorption is from 0.4 to 1.5 ml/g. The determination of the pore size and volume and their distribution is carried out in accordance with DIN 66134 of February 1998 and DIN 66133 of 1993, published by the Deutsche Institut fur Normung e.V. [0020] If appropriate, the support can additionally have been treated with acids. [0021] The active component (A) applied to the support (S) comprises at least one compound of rhenium. Suitable compounds include the sulfides, oxides, nitrides, carbonyls, halides and acids. Particular preference is given to ammonium perrhenate or perrhenic acid and rhenium heptoxide. The rhenium component can be applied to the support material by all customary methods, preferably to the finished shaped support bodies. These include, for example, methods such as impregnation in an excess of solution, "dried impregnation" (i.e. calculated according to the particular water absorption), sublimation (especially for carbonyls). If necessary, water is preferably used as solvent for the rhenium component, but it is also possible to use organic solvents such as alcohols or dioxane. In addition to the rhenium component, the active component (A) can further comprise a promoter, i.e. one or more further compounds which optimize the activity or selectivity of the finished catalyst. These compounds are selected from the group consisting of phosphorus oxide, Fe.sub.2O.sub.3, tantalum oxide, ZrO.sub.2, SiO.sub.2 niobium oxide, molybdenum and tungsten compounds, oxides of the elements of the lanthanide series, vanadium oxide, alkali metal, alkaline earth metal, lead and tin compounds. These compounds can be applied before, after or simultaneously with the rhenium component. [0022] The proportion of active component (A) in the supported catalyst is usually from 0.1 to 30% by weight. As active component, preference is given to rhenium oxide in an amount of from 0.5 to 15% by weight. The rhenium oxide is particularly preferably present in crystallites smaller than 1 nm on the surface. This corresponds to rhenium surface areas (determined by means of N.sub.2O chemisorption) of greater than 0.4 m.sup.2/g, as described in DE 19,837,203 for coated catalysts. [0023] In the supported catalyst of the invention, the total pore volume measured by means of mercury porosimetry in the range from 300 to 0.003 .mu.m is generally greater than 0.2 ml/g, preferably 0.3 ml/g, particularly preferably 0.5 ml/g, and the sum of the surface areas of these pores is greater than 30 m.sup.2/g, preferably greater than 130 m.sup.2/g, but less than 250 m.sup.2/g. The determination of the pore size and volume and their distribution is carried out in accordance with DIN 66133 of June 1993 and DIN 66134 of February 1998, published by the Deutsche Institut fur Normung e.V. [0024] The production of the catalyst of the invention can be carried out in three different ways. [0025] The first method has already been mentioned above in the description of suitable supports (S). Here, the supports (S) having a maximum of the distribution function of the pore diameter in the mesopore range at from 0.008 to 0.050 .mu.m are used and the supported catalysts are otherwise produced by customary methods. [0026] The second method comprises [0027] a1) in step (a1), producing a raw mixture (a) comprising a finely divided support (S) onto which a customary active component may have been applied if appropriate, a pore-forming material (P), customary auxiliaries and if appropriate a customary active component, [0028] b1) in step (b1), forming shaped bodies as are customary for supported catalysts from the raw mixture (a) and, either simultaneously or in a subsequent separate procedure, removing the pore-forming material (P) by heating, [0029] c1) in step (c1), if appropriate applying an active component (A) to the shaped bodies, with the step (c1) being obligatory if the production of the raw mixture (a) in step (a1) has been carried out without using the active component (A) or a support (S) to which an active component (A) has already been applied and otherwise being optional. [0030] The abovementioned sequence of steps encompasses the embodiments: (i) the total amount of the active component (A) is used in the raw mixture (a) in step (a1), either as a result of it being added separately to the raw mixture (a) or as a result of it having previously been applied to the customary support (S), (ii) only part of the total amount of the active component (A) is used in the raw mixture (a) in step (a1), (iii) the active component (A) is not yet used in the raw mixture (a) in step (a1). In the case of embodiment (i), step (c1) is unmeasured. In the case of embodiment (ii), it is necessary to add the missing part of the active component by means of step (c1). In the case of embodiment (iii), it is necessary to use the total amount of the active component (A) in step (c1). Continue reading about Supported catalyst with a defined pore distribution in the mesopore range... 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